Clipboard Viewer Component
| Release: | 1.4 | ||||||||||||||||||||||||||||
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| Date: | 13 October 2010 | ||||||||||||||||||||||||||||
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Delphi Compatibility:
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- Overview
- Download
- Install Info
- Change Log
- License
Overview
TPJCBView is a non-visual Delphi component which registers a hidden window as a "clipboard viewer".
This means that Windows notifies the component whenever the clipboard contents change. On receipt of these notifications the component triggers an event. By handling the event your application can respond to changes on the clipboard. The component can be used as the heart of a program that displays "live" information about the clipboard. Alternatively it can simply enable and disable other components whose state depends on the available clipboard formats.
TPJCBView provides an Enabled property that is used to enable and disable the component and hence it's events. It also has a TriggerOnCreation property that triggers an event when the control is created.
Documentation
The component is documented in the Clipboard Viewer Component Wiki.
Users of Delphi version 3 to 7 can also make use of the help file that is included in the download. It integrates with the Delphi 3-7 help system. The help file is a WinHelp file and therefore does not work on Windows Vista and later unless WinHelp has been downloaded and installed. See Microsoft Knowledge Base Article KB917607 for further information.
Demo program
A demo program with an associated explanatory read-me file is included in the download. The demo enables and disables a button depending on if the clipboard contains text. It can also display clipboard text in a memo.
How it works
TPJCBView works by registering its hidden window with Windows. This
is accomplished by using the SetClipboardViewer API call that adds
the window to the clipboard chain. The component then handles the
WM_DRAWCLIPBOARD message that Windows sends to the hidden
window when the clipboard changes. The WM_CHANGECBCHAIN message
that indicates when the viewer chain has changed is also handled.
Two of my articles provide details of two of the key techniques used in developing this component:
- "How to get notified when the content of the clipboard changes" is self-explanatory; while
- "How a non-windowed component can receive messages from Windows" shows how to create a hidden window to enable a non-visual component to receive Windows messages.
Feedback
If you find any bugs or want to suggest a new feature please report them
using the Issue Tracker. Be sure to tag any issues as Project-cbview. If you have
created a bug fix or have implemented a new feature please attach a zip file
or diff containing your source code.
If your have any other comments please contact me.